Heel cushions have been provided heretofore in a variety of configurations and for various purposes. Mention may be made particularly of the description of a silicone heel cushion in Orthopadie Technik 11/87, pp. 654,656. A cushion of this type may be used to provide cushioning and support of the back of the foot to compensate for different leg lengths to damp shocks in walking and running, to absorb maximum impact and shock loads or the like.
In practice, it has been found that heel cushions of silicone rubber are highly desirable because this materially is relatively incompressible but is elastically yieldable.
Silicone rubbers, because of their yieldability, have been found to be particularly suitable for all of the foregoing purposes and are easily shapable to particular needs for various types of shoes.
The conventional heel cushion, however, is composed of the same silicone rubber throughout so that the properties of the material are uniform over the entire heel cushion. I have found, quite surprisingly, that this may be a drawback because the pressure distribution on the heel or lower rear part of the foot is substantially uniform. In certain regions, for example, at a heel spur or the calcaneal tuberosity, the pressure is generally much higher than elsewhere. The fact that the material has the same yieldability in the conventional heel cushion, results in a difference in the cushioning effects at the high pressure regions and elsewhere along the bottom of the heel. The result is a negative effect, especially in the case of a misstep or a particular stress upon the heel spur.